A cassette tape that is used in magnetic recording devices is composed of, for example, cassette case 1, two tape guides 2a and 2b, two tape guide posts 3a and 3b, take-up reel 4a and supply reel 4b as shown in the accompanying drawing. The tape guides are used for the purpose of maintaining the position of magnetic tape constant to ensure safe and smooth run of the magnetic tape on the magnetic recording devices.
Conventionally employed tape guides are usually made of hard chrome-plated stainless steel having a surface roughness of 0.5 .mu.m or less. However, a demand for less expensive tape guides prompted studies on use of resins as materials for tape guides, and tape guide pins made of polyacetal resins, polysulfone resins, and the like have so far been developed.
These resin tape guides, however, fail to effectively dissipate the heat produced by friction with the magnetic tape due to their low thermal conductivity, which results in significant heat accumulation. Therefore, fears are entertained as to deformation of tape guides or adverse influences on magnetic tapes due to generation of thermal stress.